1. Field of the Invention
The present invention relates to an electronic device such as a semiconductor device or the like and a method for manufacturing such an electronic device, specifically to an electronic device and a manufacturing method therefore in which a molding is provided with a protection layer applied over the entire body of the electronic device.
2. Description of the Prior Art
Conventionally, an electronic device such as a semiconductor device or the like is wirebonded and a molding material is applied over the entire body of the electronic device.
Generally, in a plastic molding package, water which reduces the reliability of the electronic device enters the molding from external sources, and has a tendency to collect on the rear or under side of the die of the lead frame. Then this moisture vaporizes quickly when the package is soldered (this generally involves immersion in molten solder at 260.degree. C. for 3 to sec). As a result, the molding which is softened by this heating swells, so that cracks or bulging are induced in the molding itself.
A conventional semiconductor device as shown in FIG. 1 comprises a lead 35 and a die 35', an IC chip 28 die-attached to the die 35' and a molding 41.
The frame die 35' is made of metal such as copper, 42 Alloy (which is an alloy comprising nickel and iron, with the ratio of nickel to iron 42:58) or the like, on the surfaces, specifically on the under or reverse side, of which a low class oxide 32 is inclined to be formed during heat treatment at 100.degree. C. to 350.degree. C. when the electronic part 28 is die-attached to the die 35' through a paste layer 24.
For this reason, if the molding process is performed using an organic resin to form a molding 41 immediately after the die-attaching, an extremely easily-peeled oxide layer 32 remains between the molding 41 and the copper or 42 Alloy. When this electronic device is stored for a long period, the moisture from the air is absorbed by the molding 41 and the moisture is accumulated in the vicinity of the oxide layer 32. For this reason, it is unable to withstand the sudden thermal shock that occurs when solder is subsequently applied for 3 to 10 sec at 260.degree. C., and cracks 33, 33' are produced in the molding 41 around the periphery of the die 35'. In addition, the moisture collected on the rear side of the die 35' is converted to steam and a void 50 occurs at that point, so that swelling 41' (the phenomenon of swelling occurs because the water in the vicinity of the die 35' turns to gas as a result of the temperature elevation when solder is applied to the molding 41 on the rear side of the die 35' ) occurs on the under or rear side of the molding 41. Then, for long time use after it is mounted on a printed-circuit board (PCB), the entry of water and impurities at the location of the cracks induces a deterioration in the characteristics and reliability of the semiconductor device.
In addition, in the prior art, the molding 41 is made from an insulating material of organic resin with a high specific resistance of 1.times.10.sup.17 .OMEGA.cm or greater, therefore, at time of assembling using surface mount technology (SMT), static electricity accumulates on the surface of this insulated molding material through the contact with a jig surface or during storage. When this organic resin is thick, the electric field strength in the mold is relatively small, and the electrostatic discharge damage of the electronic parts does not often occur. However, when the thickness of the molding material is 1.5 mm or less, the strength of the electric field of the static electricity becomes relatively large, and, it can not be ignored from the aspect of guaranteeing the reliability of the electronic parts.